ABSTRACT The Multicenter AIDS Cohort Study (MACS) and the Women's Interagency HIV Study (WIHS) Combined Cohort Study (CCS) is a large, comprehensive, prospective cohort study designed to investigate a spectrum of questions relating to the basic science, clinical science, and epidemiology of HIV infection in the US, with a focus on comorbidities among men and women living with HIV. The purpose of this application is to support the Data Analysis and Coordination Center (DACC) for the CCS. The specific aims of the DACC are: 1) To optimize the contributions of the MACS and the WIHS to the understanding of the pathogenesis and treated history of HIV infection in U.S. adults by providing epidemiological and statistical expertise, and initiating and sustaining successful scientific partnerships, to support the unified science agenda; 2) To coordinate the recruitment of 2,500 new MACS/WIHS-CCS participants, including coordination of the administration of standardized baseline visits across all clinical research sites and integration of data from new recruits with the existing combined database; 3) To coordinate research initiatives and scientific presentations; to facilitate communication amongst CCS and external investigators, Working Groups and committees; to orchestrate study protocol and form revision; to coordinate outcome ascertainment and adjudication of clinical events; and to disseminate key scientific findings; 4) To develop and maintain a web-based data management system to harmonize and integrate data from the MACS and WIHS, as well as manage new data collected per the CCS protocol. We will continue our systems for: tracking the storage and transfer of biological specimens at national repositories, producing annual public data sets, and conducting training in methods that facilitate the appropriate use of study data for local research; and 5) To continue our quality assurance program in partnership with the clinical research sites that integrates expertise in data management, study coordination, statistical methodology, and scientific disciplines.